I think it is more likely that black women/pr women are more secure with themselves, and feel less needy. White girls seem to feel more lucky to have a guy to suck off while the black/prs feel like the guy is lucky to be with them. Kind of like how fat black chicks always think they are hot even though they look really nasty. They'll still expect you to go down on them but they won't reciprocate.
I've done a pretty good sampling across the racial boundaries and typically I find the more a woman is into me the more likely she will do it. Simple fact is if the sexual relationship is a car, who's behind the wheel, if you're driving chances are she's sucking you more than you're licking her.
One thing you have to consider is that if you straight up ask women most are not going to answer truthfully, but behind closed doors where they know you aren't going to disrespect them after or make whatever happens public knowledge most women will do pretty much anything.
Typically if I'm with a woman, no one knows about it unless she tells her friends or mine. Discretion will allow a woman to open up to you in many many ways.
